Electrical connecter plug



March 17, 1936. E, lTH 2,034,272.

ELECTRICAL CONNECTER PLUG Filed Sept. 29, 1930 INVENTOR JOHN E. MIT/ 5% ATTO'RNEY Patented Mar. 17, 1936 PATENT: OFFICE ELECTRICAL CONNECTER PLUG John E. Smith, Plainfleld, N. ,J., assignor a Knapp-Monarch Company, a corporation of Missouri Application September 29, 1930, Serial lilo-484,950

4 Claims. 01. 177-311) My invention 1 relates to electrical ,connecter plugs, and is shown as more particularly applied 1 to that type of plug intended to be detachably connected to electrical appliances.

It is one object of my invention to provide in a .plug of the above indicated character means for visibly indicating when the circuit from a source of current supply is completed through the electrical element of the appliance. In other words, if the circuit through the appliance element is defective, the indicator will not show a cchnpleted circuit. a

It is another object of my invention to locate a tell-tale light within the connecter plug,' but visible therethrough, and to arrange the con-' nections so that a-lamp of low voltage can be used.,

It isa-further object of my invention to provide a connecter plug with a tell-tale light lo- 2o cated within the plug, the plug being arranged so that the lamp may be readily removed and in- ,sertedin the plug without .the necessity of taking the plug apart, ordisturbing any of the wiring,

connections to the'plug or the lamp. 1

It is a still further object of my invention. to I provide "a plug of theabove indicated character with a simple yet rugged. wiring arrangement especially adapted for the aforementioned purposes. 30 .It; is a still further object of my invention to provide a plug having a removable indicator lalmp and a guard for said lam'pcarried by said 1 s- It is a still further object of my invention to provide a resistor in circuit with an electric',ap.- pliance and to connect. an indicator lamp across said resistor. p

It is a still further object of my present invention to provide an electrical connecter plug having a signal of the type shown in my-cm pending application's serial No. 499,701, filed,

December 3, 1930' and Serial I lo. 643,620, filed November 21, 1932, the latter of which is a division from the present application.

Other and further objects of 'my invention will be apparent from the following specification takenhin conjunction with the 'acompan'ying drawing, wherein- Figures 1, 2 and 3 are respectively front, rear I 50 and side views of my improved connecter plug; Figure 4 is a plan view of my improved plug, the top half being removed so as to facilitate the illustration; v

Figure Us a longitudinal section taken on the line 5-: arms. 1;

Fig. 6 is a detail of one of the connecter clips;

and 1 Fig. 7 is a diagram showing the circuit connections to and in my improved connecter plug.

Arrangements heretofore proposed for the use 5. of tell-tale lights on electrical appliances, such aselectric irons, percolators, or electric heaters, have merely been indicators that the current had been turned on in the connection cord connected to the appliance. If the heating element in the 1 d appliance should be burned out, or the connections to the heating element broken, the light would nevertheless continue to indicate the current being turned on at the wall plug or lamp socket, or in the connection cord. By my pro- 15 posed arrangement, the lighting of the indicator lamp depends upon the circuit through .the electrical appliance. Hence, if the circuit through the appliance is not established or coinpleted there will be no indicator light. Thus, my

In order to protect the lamp from damage by being in an exposed position, I arrangethe lamp within the body of the connecter plug. However,

- it is not practical to usea 110 volt lamp in'.

the connecter plug, even if it were practical to get alamp of such a voltage in the confined area of the body 01 the plug, for the reason that the heat of the'lamp would be so great it would affect the material of which theplug is composed, and v perhaps cause other damage to'the connections,

as well as rendering the plug uncomfortably hot 40 to handle. g

Therefore, I propose to use an ordinary flash light bulb requiring but 2 to 3 volts and drawing but 200 milliamperes .of current. such a ,low

wattage lamp will generate practicallynog-heat. and certainly none of a serious character, within the. confined space permitted on the interior of a connecter plug. I

I am enabled to use such a low voltage lamp 4 by connecting the same about a resistor so as to take the drop thereacross, the resistor being, in

series circuit with the circuit through said appli a'nce. However, it is important that the resistor shall not be confined within the bodyof the plug for it is, apparent that the energy consumed 85 l 'igm'e 7) oi-an appliance. However, the clip '5 outside the plug, as for instance within the connecting cord extending between the wall outlet and my improved connecter plug.

Inasmuch as the indicator .lamp may burnout and therefore need replacement, -I provide an '10 opening in one-halt oi. my improved connecter plug through which the concealed lamp may be removed, and a fresh lamp inserted, and over vthe opening I provide an aperttired guard.

Referring now to Figures 1 to'6 of the drawing,

lo niy improved plug is i'ormed of two pieces, an

upperhalt ll and-a lower half l2. All of the electrical connections in the plug are located in d the lower half of the plug, the connectingstrips,

25 lieved necessary to describe in detail the lower;

etc., being embedded in appropriategrooies or 20 channels. Wherever it is necessary. the upper halt II has complementry grooves or channels cooperating with those oi. the lower half to propthis is the usual practice in this art, it is only behalf of the plug, shown in Fig. 4.. v

At the reduced end i2 01' the plug, there are 10- catedtwochannels l4 andl5 terminating in openings at the end of the plug. In these chan- 30 nels are embedded'sprlng clips. l8 and I1 respectively. These clips may be of any 01' the usual and well known constructions adap .the projecting pins I64: and Ila ordinarily constitutlng the terminals oi a heating element E- (see I! is provided with an extension It, the purpose oi which will be more fully hereinafter set forth.

. The channels II and "are of a considerable depthto aikommodate the clips l6 and II, but

to theflat, terminal portion la 01 each clip rests in :agoiovethat is only deep enough to accommo- A pair or, metal strips 2i and 22 join respectivelywiththe terminals." of the spring clips l5 and.

is H, the screws 23 serving to hold the strips and the terminals in electrical engagement with each other. The screws engage in screw threaded bushings, not shown, which bushings are embedded in the bakelite or other material oiZwhich" I 50 the plug is composed. The connecting strips 2| and 22 rest in appropriate channels or grooves of a shape and size to accommodate the strips; which terminate respectively at terminal screws 24 and 25. It will be noted that the strips 2| and 55 22 extend longitudinally of the plug adjacent the o posite side edges thereof. Between the channels for these strips is located an enlarged out out portion or pocket 26 adapted to house an indicator lamp 21.

60 Theindicator lamp 21 comprises a bulb 22,

which is shown as rounded, housing a filament 29.

Such lamps are ordinarily provided witha screw-1 threaded metallic shell 3| on the base portion constituting one of the terminals of the filament 65 25. A terminal 32 on the end of the base constitutes the otherterminal for the filament '29. the it and 32 being insulated from each o I 1 The base 01' the lamp 2'! is received in a substantiallysemi circ spring clip 33 (Fig. 5) which has a metallic's p 24 secured thereto.- It will be noted that the strip 34 rests on the bottom oi the pocket 26 and passes under the connecting strip22, where it bridges the pocket 26, entering 75 an inclined groove 35 which leads upwardly from toengage.

spring clip 23. ,1

the bottom or the pocket 2,: and terminates at the-third terminal screw, 25, that is located at the opposite side edge of the plug from the terminal screw 24. 4 p

It will be noted that the connecting strips 2| and 22 bend to the left while connecting strip 24 bends to the right in orderto properly space the- M the opening 42 at the endat the plug. The-three wires are indicated in Fig. 7, wire ll being the usual copper wire conductor extending along with each other adia I groove 42 and. terminating under the terminal screw 24, thus establishing electrical connection with the connecting strip 2| and spring clip l6.

Wire 44 in the connecting cord, likewise a copper conductor, extends along groove 45 and terminates v under the terminal screw 26 thus establishing erly enclose the plug and its connections. As electrical contact with. the connecting strip 24 that is connected to one side ot the lamp 21.

The thirdjwire of the connecting cord is indicated'at 45. This is a resistance wire chosen to have a predetermined ohmic. resistance, the IR drop across which corresponds to the voltage required to properly energize the lamp 21. I

have found that the iiash light lamp requires but making electrical connection with the connecting strip 2: directly to the clip n The other connection for the lamp ,2! is 121- dicated generally in the diagram at 48, and in the plug extends from the terminal 32 otithe lamp to the clip II. In my improved plug this connection is combined with means for holding the lampinpositioninthe plugaswillnowbedescribed.

Communicating with the pocket 25 is a cylin,-

drical bore 5| which is made of a size and length suflicient to receive the coiled spring, At one end the spring -52 is closed by a plate 52 against which the terminal 22 01. the lamp rests when the lamp is in place. At its other end the spring 52 rests-against-proiection 54, which is part of the arm I8 bent at right angles thereto and ex-- tending down into the end oi bore-5l Thus, the electrical connection is made from the terminal ll of the clip I! through the arm l8, theturned down portion 54, spring 52, plate 53, tothe terwhich is'designated generally at 45 in the circuit diagram of Fig. '7.

A projection 55, at the opposite end 01 the press the coiled spring ,52. The-lamp 21 is held firmly from movement longitudinally oi the plug by this arrangement, andit is held Irom movement sidewlse of the plug by the semi circular 60 minal 32 'of the lamp. This is the connection I The connecter plug of the above general character is usually provided with a coiled spring guard (not shown herein) about the connecting cord where it enters the plug at the opening 42. The end of this coiled spring is usually secured between the halves I I and I2 in an annular groove near the opening 42, and I have indicated such a groove at 56. The two halves of the plugs II and I2 are held together by two or more screw bolts indicated at 51, these passing through appropriate holes 58, extending through the halves of the plug and located in the parts that are thickest, that is to. say, where there are no which the lamp 2] is retained, so that the illumination of the lamp can be seen from all sides of the plug.

In order that the lamp may be removed from the plug without removing the bolts 51, I make the opening 6 la in the front of the plug sumciently large and circular to permit the passage of the lamp 21 therethrough. Over this opening I provide a grill or guard 64a which is riveted to the outside of the upper half II of the plug, as indicated at 650.. The riveting is intended to hold the grill or guard 64a infrictional engagement with the surface of the plug II so that itmay be pushed aside, pivoting on the rivet, to permit the lamp to'pass through the opening 6 la'. A stop 66 is provided on the plug along one edge of the guard 64a, so as to limit its movement in one direction.

When it is desired to replace the lamp 2i in the plug, any instrumentality such as a match may be inserted in the rear aperture 62a to press the bulb 28 upwardly and out throughthe opening Ma after the grill 55a has been moved out of the way. Here, aperson taking hold of the bulb 28 with his fingers can readily extract the same from the plug. A fresh lamp is reinserted through the opening tic so that the base thereof engages in the clip 33, whereupon a simple pressure upon the lamp 21 with'the finger will force the lamp home, the rounded surface 'of the bulb 28 serving as a cam on the abutment 55 to push the lamp 2? longitudinally in the clip 33 and to causeengagement of the terminal 32 on the lamp with the plate 53. After the lamp is inserted in place, the grill 64a is returned over the opening 5i.

By the foregoing, it will be seen that I have provided a construction by which will be accomp'ished the objects of the invention hereinbefore set forth in a practical manner with a simple arrangement that will be economical to manufacture.

Modifications may be made in the arrangement and location of parts within the spiritand scope of my invention, and such modifications are intended to be covered by the appended claims.

through one end of said plug, one of said clip terminals having an arm projecting therefrom, terminal screws located adjacent the .,opposite end of said plug, connecting strips between said screws and clips, an opening in the plug adjacent the terminal screws, channels in said parts from the opening to at least one of said screws, electrical connecting, wires connected to said screws, a pocket in said p1 g having an opening therefrom to the exterior of said plug, a socket mounted in said pocket, a third terminal screw. mounted adjacent the other terminal screws, a connecting strip between the third screw and said socket, a third wire connected to said third screw, an electrical connection projecting from said terminal arm to said pocket, an indicator lamp mounted in said socket and engaging the last mentioned electrical connection, and openings in said plug through which the light of said lamp maybe seen. f

2 An electrical connecter plug comprising a pair of cooperating parts, a pair of clip terminals mounted therebetween and accessible through one end of said plug, one of said clip terminals having an arm projecting therefrom, a pair of terminal screws located adjacent the opposite end of said plug, connecting strips between said screws and clips, an; opening in the plug adjacent the terminal screws, channels in said'parts from the opening to at least one of said screws, a pair of electrical connecting wires connected to said screws, one of said wires including a resistor, a pocket in said plug having openings therefrom to the exterior of said plug, a socket, mounted in said pocket, a third terminal screw mounted adjacent the other terminal screw, a connecting strip between the third screw and said socket, a third wire connected to said third screw and to the said one of said pair of wires including the resistor, appropriate screws in the body of said plug for said wires and connecting strips, a resilg ient member connected to said terminal arm and projecting into said pocket, an indicator lamp Jmounted in said socket so as to engage the re- J silient member and an abutment in said pocket for engaging the lamp to position the same in said pocket.

3. An electrical connecter plug and cord set comprising a plug body having first and second appliance engaging prongs at one end thereof and first, second and third terminals at the other end thereof, said first and second terminals being electrically connected with said first and second prongs respectively, a signal light within said plug body and electrically connected in series with said third terminal and said second prong and r a three-wire cordhaving the inner end of one wire thereof connected with said first terminal, the inner end of the second wire thereof connected with said second terminal, the outer ends of said first and second wires being adapted'for connection to a source of current supply, the outer end of the third wire thereof being connected with the outer end of thesecond wire and the inner end of the third wire being connected with said third terminal to thereby shunt a fractional part of the current flowing through an appliance having its heater element connected with said prongs from said second wire so that the shunted current flows through said signal light and the signal light is therefore energized only when said electrical connecter plug is electrically associated with such an appliance and the circuit through the appliance is complete, said second wire including a resistance sufficient to cause a voltage drop of suflicient magnitude to cause said signal light to be readily noticeable.

4. An electric connecter plug and cord set comprising a plug body having first and second epthereoi'la signal light within said plug body and i discernible from the exterior thereoi' and a'threewire cord having the inner end 01 one wire of said cord connected directly with one of said prong engaging terminals and having the second d third wires thereof connected together at e outer end 01' the cord, the inner ends of said second and third wires being connected, the second one through said signallight'with the other or said prong engaging terminals and the third one direct with the other prong engaging terminal to thereby shunt a fractional part 01. the

current flowing through an appliance having its prongs connected with said prong engaging'terminals from said third wire so that the shunted current flows through said second wire and said signal light and the signal llghtds thereby energized. only when said electric 'connecterplug is electrically associated with such an appliance and the circuit through the appliance is complete, said third wire including resistance sufllcient to cause a voltage drop oi enoughmagnitude to cause said signal light to be readily noticeable.

" JOHN E. SMITH. 

